6 eggshells
1 tsp. flour
1 tsp. very hot tap water
Clean, smooth rock
2 dishes
Spoon
Strip of paper towel
Sidewalk or playground

Wash and dry eggshells. Grind them outside on clean, smooth concrete with a smooth rock. Rind until you have a powder. Pick out big pieces of shell and throw them away. Measure flour and hot water into another dish. Add 1 tablespoon of the eggshell powder. Mix and mash until it sticks together. Shape and press firmly into a chalk stick shape. Roll stick up tight in strip of paper towel. Dry for 3 days until rock hard. Write with chalk, erase with shoe.